1. Field of the Invention
The present invention relates to a method and apparatus for searching for an active pilot in a mobile communication access network. More particularly, the present invention relates to a method and apparatus for searching for an active pilot of a home cell so as to provide a service differentiated from that of a public network in the cdma2000 1xEV-DO and cdma2000 1xRTT access networks.
2. Description of the Related Art
Active research is ongoing on technologies related to high speed data transmission in a Code Division Multiple Access (CDMA) mobile communication system. A 1x Evolution-Data Only (1xEV-DO) system is a conventional mobile communication system having a channel structure for the high-speed data transmission. The 1xEV-DO system is a mobile communication system supporting the standard proposed in 3rd Generation Partnership Project 2 (3GPP2) to make up for the shortcomings in the IS-2000 system.
In the cdma2000 1xEV-DO and cdma2000 1 xRTT mobile communication access networks, an access terminal or mobile station selects an active pilot for monitoring by considering only pilot strengths. In doing so, the access terminal receives an overhead message from the cell that it is monitoring, and receives information on the corresponding cell and information on neighbor cells using the overhead message. A configuration of such cells is shown in FIG. 1.
FIG. 1 is a diagram illustrating a configuration of an access network in a mobile communication network in which public cells and home cells coexist. FIG. 2 is a flowchart illustrating a method in which an access terminal searches for an active pilot for monitoring, in a conventional mobile communication network.
Referring to FIG. 1, home cells Ph1 to Ph23 exist in public cells Ppub1 (110), Ppub2 (120), and Ppub3 (130). In the mobile communication network of FIG. 1, a general access terminal searches for an active pilot according to the procedure of FIG. 2.
Referring to FIG. 2, in step 200, the access terminal searches for a pilot in an access network where public cells and home cells coexist. In step 210, the access terminal measures strengths of pilots P1, P2 and P3, and determines the strongest pilot Pstrongest among them. In step 220, the access terminal determines whether the strength of the strongest pilot Pstrongest is greater than a minimum pilot strength Pmin. If the strongest pilot Pstrongest is greater than the minimum pilot Pmin, the access terminal sets Pstrongest as the active pilot Pa in step 230. Otherwise, the access terminal returns to step 200. In step 230, the access terminal receives an overhead message from a cell corresponding with the strongest pilot Pstrongest. If there is a request for new pilot search in step 240, the access terminal returns to step 200 and repeats its succeeding steps. Otherwise, the access terminal returns to step 230.
As described above, in the conventional cdma2000 1xEV-DO and cdma2000 1xRTT access networks, the access terminal selects an active pilot for monitoring by considering only pilot strengths. Therefore, in the access network where public cells and home cells coexist, even though a user is located in the service coverage area of the home cell in which it is registered to receive a differentiated service, and the strength of a pilot for the home cell is high enough to receive the service, if the strength of a pilot of a neighbor public cell is higher than the pilot strength of the home cell, the home cell cannot provide a stable and satisfactory differentiated service because the service will not be based on the pilot of the home cell. In addition, while monitoring a public cell or a home cell using the active pilot, the access terminal cannot provide information indicating the possibility of the service differentiated from that of neighbor cells, and therefore has difficulty in providing the differentiated service.
Accordingly, there is a need for an improved method and apparatus for searching for an active pilot of a home cell so as to provide a service differentiated from that of a public network in a mobile communication access network.